The use of movable cursors on display devices of aircraft flight decks is known. To provide redundancy, some aircraft provide a primary cursor control device such as a trackball and alternate means of controlling the cursor such as directional movement keys on a keyboard. The directional movement keys may be used when the use of the primary cursor control device may not be practical such as during episodes of turbulence.
Existing methods of controlling the movement of a cursor using directional movement keys can require significant pilot workload due to the concentration and attention required to position the cursor adequately. For example, some methods comprise stepping the cursor by a fixed distance in a desired direction each time a directional movement key is actuated. This can results in a large number of key actuations being required if the fixed distance is small and the target position is far from the initial position of the cursor. Alternatively, if the fixed distance is large and the target is close to the initial position of the cursor, there may be a risk of jumping over the target position. Some existing methods also use slewing of the cursor at a constant speed when a directional movement key is actuated and held. Slewing can take a relatively long time to move a cursor to the desired target when the target position is far and can also require sustained attention of the pilot to achieve adequate positioning of the cursor.
Improvement is therefore desirable.